A glow discharge starter is usually connected across or in parallel with an arc discharge lamp and contains a pair of electrodes. At least one of the electrodes comprises a bimetallic element which, when heated as a result of the glow discharge, bends towards the other electrode. When contact is made, the glow discharge ceases causing the bimetallic element to cool and withdraw from the contacted electrode. When contact is broken, a voltage pulse induced by the induction of the ballast, appears across the opposed electrodes of the lamp thereby initiating an arc discharge within the lamp. If the lamp ignition does not occur after the first voltage pulse, the glow discharge starter sequence is repeated until lamp ignition occurs.
A glow discharge starter of the aforementioned type is described, for example, in the book "Light Sources" by Elenbaas, Philips Technical Library, pages 102-103. Other types of glow discharge starters are shown in U.S. Pat. Nos. 2,930,872; 2,930,873; and 3,887,847.
Glow discharge starters, included as part of an arc discharge lamp, are shown in U.S. Pat. Nos. 4,117,370; 4,144,475; 4,277,725; 4,377,771, and 4,374,339.
It is known to include a getter within the glow discharge starter, for example, to prevent breakdown or to remove deleterious gases that may form during processing or during operation of the glow discharge starter. U.S. Pat. No. 4,377,771 shows a starter containing a reversible getter which gives off a gas when the temperature increases and absorbs the gas when the temperatures decreases.
Many commercially available glow discharge starters contain a getter holder centrally located at the end of the starter envelope remote from the exhaust end or stem press. The getter holder consists of a small piece of metal in which a cup is formed therein. The cup contains a getter mixture which, for example, may comprise barium, magnesium and thorium. During fabrication and processing, the getter mixture contained within the cup of the getter holder is "flashed" onto the internal surface of the envelope and internal parts of the glow discharge starter. Flashing is a known process accomplished by means of a radio frequency generator commonly referred to as a bomber. The above mentioned process creates a more effective surface area for improved gettering of deleterious gases within the glow discharge starter. An example of the above mentioned glow discharge starter is the GB-HS starter manufactured by GTE Sylvania S.A. in San Jose, Costa Rica.
It was observed that the life of the glow discharge starter is a function of the residual gas content contained within the starter envelope. It was discovered that during operation of the glow discharge starter of the type described above, components of the fill gas are entrapped by the residual getter mixture remaining in the getter strip cup after flashing. The interior of the getter strip cup after flashing resembles a pitted and cracked surface composed of residual getter components. It is speculated that the catalytic activity, adsorption or absorption of the residual getter mixture remaining in the cup, may be enhanced by the increased surface area resulting from the crevices, edges and corners produced within the cup. It is also speculated that the created glow discharge in the glow discharge starter leads to ionization of the rare gases contained in the starter envelope. The ionized gases may then be accelerated (owing to the applied potential across the glow discharge starter electrodes) into the relatively high surface area of the residual getter remaining in the cup which is positioned within the main glow discharge. Entrapment of the fill gas components in the residual getter mixture results in early glow discharge starter failures.